On Tue, Feb 20, 2018 at 02:25:03PM -0800, Linus Torvalds wrote: > On Tue, Feb 20, 2018 at 1:01 PM, Dominik Brodowski > <li...@dominikbrodowski.net> wrote: > > +ENTRY(interrupt_entry) > > + UNWIND_HINT_FUNC > > + > > + PUSH_AND_CLEAR_REGS save_ret=1 > > + ENCODE_FRAME_POINTER 8 > > + > > + ret > > +END(interrupt_entry) > > There's nothing wrong with this patch, but it does expose what a nasty > hack our "ENCODE_FRAME_POINTER" thing is. > > It generates (when there is an offset, like this): > > leaq \ptregs_offset(%rsp), %rbp > orq $0x1, %rbp > > and I would _really_ hope that the stack pointer is always aligned on > interrupt entry, so I don't see why it's not just > > leaq 1+\ptregs_offset(%rsp), %rbp > > instead. > > I dunno. Let's ask Josh what the reason for the separate "or" was. > > But this is an independent issue of this patch, really.
Indeed, how about this? ---- From: Josh Poimboeuf <jpoim...@redhat.com> Subject: [PATCH] x86/entry/64: Simplify ENCODE_FRAME_POINTER On 64-bit, the stack pointer is always aligned on interrupt, so instead of setting the LSB of the pt_regs address, we can just add 1 to it. Suggested-by: Linus Torvalds <torva...@linux-foundation.org> Signed-off-by: Josh Poimboeuf <jpoim...@redhat.com> --- arch/x86/entry/calling.h | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-) diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h index dce7092ab24a..400cea8bbf4b 100644 --- a/arch/x86/entry/calling.h +++ b/arch/x86/entry/calling.h @@ -172,12 +172,7 @@ For 32-bit we have the following conventions - kernel is built with */ .macro ENCODE_FRAME_POINTER ptregs_offset=0 #ifdef CONFIG_FRAME_POINTER - .if \ptregs_offset - leaq \ptregs_offset(%rsp), %rbp - .else - mov %rsp, %rbp - .endif - orq $0x1, %rbp + leaq 1+\ptregs_offset(%rsp), %rbp #endif .endm -- 2.14.3
